Most current immunological models assume that superantigens activate T cells by simultaneously binding MHC class II molecules on antigen-presenting cells and the Vb element on T cells. However, no structural information is available on the interactin of superantigens with TCRs. If we can get our crystals to diffract to better than 3 w resolution, we would be able to examine the superantigen-TCR interface in some detail as well as address the issue of possible conformational changes in the b chain and/or the superantigen upon binding.